I've not tried it over 10m for basic 1080p, but I had real problems running at 4K at anything over 3m. And the 5m Lindy copper cables I tried were more expensive than 10m fibre-optic ones are now!
Where fibre-optic cables really come in is conference rooms and trade stands. In conference rooms the projector is often in the ceiling whereas the controlling PC is often in a cupboard, so you need 10-20m (maybe more) of video cable to link the two. On trade stands the PC is often secured out of sight with only the monitor, keyboard, and mouse in stealable locations. It's the security of the company data that's at issue; the cost of the PC is relatively trivial.
For the home enthusiast, you've spent hundreds of pounds (maybe a thousand!) on your super-duper GPU. You've spent hundreds of pounds (maybe a thousand!) on your super-duper monitor. Why baulk at spending under a hundred on the the thing that lets the two work together in that super-duper way?